The present invention to a novel stent delivery system in the treatment of occluded blood vessels.
Percutaneous transluminal coronary angioplasty (PTCA) has proven to be a successful technique in the treatment of stenotic arteries and vessels, particularly those found in the human heart. In fact in certain cases, this treatment has served as a substitute for coronary by-pass surgery. During PTCA procedures, a catheter is inserted through a large artery in the leg or arm of the patient and is directed into an occluded vessel, such as a coronary artery. The catheter also carries an inflatable balloon which forces open the obstruction, normally in the form of a plaque material. In addition to the use of such balloon angioplasty procedures, stents have been developed to maintain the dilated vessel in an open condition. The use of stents has prevented subsequent closures of vessels referred to as xe2x80x9crestenosisxe2x80x9d, due to scarring, the accumulation of plaque and the like.
A particularly vexing situation occurs in vessels which include a branching arrangement. Such situation is referred to as a bifurcating vessel, i.e. where a main trunk vessel meets a side branch vessel. The angle between the main trunk vessel and the side branch is usually referred to a xe2x80x9ccarinaxe2x80x9d. Carinas may be acute, orthogonal, or obtuse. In a bifurcating vessel situation, the side branch often includes lesions similar to that of the main trunk branch. Insertion of a stent in the main trunk vessel alone, following dilation, is not satisfactory, since the side branch lumen is blocked. Stents must be placed in the main trunk vessel as well as the side branch to properly rectify occluded vessels in a bifurcating vessel.
Systems have been proposed for stent placement in bifurcating vessel. For example, the U.S. Pat. Nos. 5,632,763; 5,669,924; 5,720,735; 6,033,434; 6,056,775; and 6,117,117 show stent devices and procedures in which separate stents are placed in the main trunk vessel as well as the side branch of a bifurcating vessel. In most cases, a pair of guide wires is employed to separately direct distinctive stents in each of the portions of the bifurcated vessel.
U.S. Pat. Nos. 4,994,071; 5,755,771; 6,033,435; 6,086,611; and 6,099,560 show stent systems in predilated bifurcating vessel situations which use forked stents. These forked stent derive from a main stent body and include pairs of end stents that are expandable from a side-by-side parallel configuration to an angular configuration for insertion into the main trunk vessel and side branch.
A stent system which is adaptable for use in a bifurcating vessels of varying angular configurations would be a notable advance in the field of percutaneous transluminal coronary angioplasty.
In accordance with the present invention a novel and useful stent system for emplacement in a branched vessel is herein provided.
The stent system of the present invention utilizes a stent unit having a first portion including a wall which forms a first lumen through the same. The first portion is constructed of material permitting the expansion of the wall between an initially collapsed configuration and an extended position. For example, the first portion of the stent unit may be composed of articulating stents which expand under pressure, a structure known in the art. Such change in configuration is accomplished by the use of mechanical forces applied to the first portion. In the latter case, expansion is achieved by the use of an expanding balloon used in angioplasty procedures.
A second portion is also included in the stent system of the present invention. The second portion possesses a wall forming a second lumen. The second portion is constructed of a material which is similar, but more rigid than, the material of the first portion. Thus, the second portion exhibits the same expansion characteristics, but expands under a higher applied pressure due to the nature of the construction material with respect to the first portion. The second lumen of the second portion communicates with the first lumen of the first portion. Also, the wall of the second portion is contiguous with the wall of the first portion. In this regard the first portion may be configured to form a recess which is at least partially occupied by the second portion when the stent unit is in its collapsed position. In addition, the wall of the first portion forming the recess may be constructed of a less rigid material than the remainder of the first portion. Such configuration permits the expansion of the recess portion of the first portion under a lower pressure than the remainder of the first portion of the stent unit. The second portion is also capable of unseating and protracting from the recess of the first portion, when the stent system is inserted in a bifurcating vessel, during expansion. In other words, at a relatively low applied pressure, without expansion of the first portion of the stent unit, the recess expands to unseat the second portion from the recess. Further application of pressure expands the remainder of the first portion. Finally additional pressure, expands the protracted second portion. In general, the main trunk or first passage of the bifurcating vessel would be occupied by the first portion of the stent unit while the second portion of the stent system would occupy the second passage or side branch of the bifurcating vessel.
An angioplasty balloons, having a bifurcated or tee configuration, may be incorporated into the stent system of the present invention. Also, other occlusion removal devices, such as those used in rotational arthrectomy techniques, are compatible with the system of the present invention, prior to deployment of the stent unit of the present invention. The operation of the stent system of the present invention will be more fully described hereinafter.
In addition to the stent unit above described, the stent system of the present invention further employs a stent delivery device in the form of a sheath having an external surface and a chamber or cavity therewithin. The sheath extends over the stent unit, resulting in the stent unit lying in the cavity of the sheath. The sheath is formed with an elongated body that terminates in an end portion. The end portion is split into first and second elements that are separable from one another. Thus, a gap may be formed between the first and second elements in this regard. In certain cases, the first and second elements of the end portion of the sheath may be formed from a material which is more flexible than the material forming the body of the sheath. Such flexibility may also be accomplished by thinning the first and second portions in the vicinity of the gap between the sheath. The sheath may also be constructed with first and second openings to pass first and second guide wires. Of course, the guide wires extend from the exterior of the body of the patient to the end portion of the sheath and through the first and second openings. In addition, it should be understood that, in a PTCA procedure, guide wires are placed or positioned in the bifurcating vessel, one in the main trunk and one in the side branch by initially entering the patient through an artery in the leg or arm by using conventional PTCA techniques. Guide wires are also positioned, in the present system, relative to the first and second portions of the stent unit such that one guide wire extends through the first lumen and the other guide wire extends through the second lumen of the same. The guide wires may be marked with indicia or coloration, which is visible externally to the body of the patient in order to keep track of the same during a PTCA procedure.
A catheter may be used to deliver the guide wires into the proper positions herein above described. The catheter may take the form of an elongated tube which includes first and second passageways terminating in first and second openings. The ends of the guide wires may be angled or bent to match the particular configuration of the bifurcating vessel prior to insertion. This permits the ends of the guide wires to be positioned in the proper portions of the bifurcating vessels. Normally, the guide wires are advanced one at a time, one wire to the main trunk followed by a second wire to the branched vessel. Of course, after positioning of the guide wires in the bifurcating vessel, the catheter is retracted from the vessel, leaving the guide wires in the proper position relative to the two portions of the bifurcating vessel. Guide wires also serve to direct the sheath for delivering the stent unit of the present invention into its proper position. That is to say, the stent unit is advanced along the guide wires within the sheath when the sheath is in place.
The present invention also entails a method for placing a stent in a bifurcating vessel in which a catheter is advanced to the bifurcating vessel using PTCA techniques. The catheter possesses two passageway terminating in two openings. The first guide wire is delivered to the main trunk followed by the delivery of a second guide wire to the branched vessel. The first guide wire utilizes the first passageway and first opening, while the second guide wire utilizes the second passageway and the second opening of the catheter. After the wire delivering catheter is retracted, and, following predilation or other plaque attenuation techniques, a sheath is extended to the bifurcating vessel site. The stent unit of the present invention lies in its collapsed position and is fitted with a deflated bifurcated angioplasty balloon. Then stent unit is then placed in the sheath and fitted over the guide wires, extending outside the body of the patient. Needless to say, the first guide wire passes through the first lumen of the stent unit while the second guide wire passes through the second lumen of the stent unit. The stent unit is advanced along the guide wires and within the sheath to the bifurcating vessel. Once the stent unit is positioned at a proper position at the bifurcating vessel, the first end portion of the sheath passes back over the stent unit by separation or peeling of the first and second elements of its end portion. The sheath is then removed from the area of the bifurcating vessel and, eventually, from the body of the patient. The stent unit is then positioned within the bifurcated vessel in its proper position along the guide wires such that the first portion lies in the main trunk and the second portion extends into the side branch. Such positioning takes place by at least partial expansion of the first and second portions of the stent unit by inflation of a bifurcated angioplasty balloon. Low pressure inflation first causes unseating and protraction of the second portion of the stent unit, relative to the recess of first portion. Higher pressure in the balloon expands the first portion. Finally, the second portion in expanded at an ever higher pressure in the balloon. The forked angioplasty balloon is then deflated and removed along the guide wires, which are also removed.
It may be apparent that a novel in useful stent delivery system and method for placing a stent unit in a bifurcated vessel has been hereinabove described.
It is therefore an object of the present invention to provide a stent delivery system and a method for placing a stent unit in a bifurcated vessel which is simple and reliable.
Another object of the present invention is to provide a stent delivery system and a method for placing a stent unit in a bifurcating vessel which employs many of the techniques known in prior PTCA treatments.
Another object of the present invention is to provide a stent delivery system and a method for placing a stent unit in a bifurcating vessel which utilizes a stent unit that very closely conforms to the configuration of a bifurcating vessel determined by the carina between the main trunk vessel and the side branch.
Yet another object of the present invention is to provide a stent delivery system and a method for placing a stent unit in a bifurcating vessel which is capable of deploying a stent in such bifurcating vessel using simplified techniques, thus reducing the trauma to the patient.
Another object of the present invention is to provide a stent delivery system in a method for placing a stent unit in a bifurcating vessel which is completely safe and maintains the patency of both branches of the bifurcating vessel.
The invention possesses other objects and advantages especially as concerns particular characteristics and features thereof which will become apparent as the specification continues.